Differentiation inducers modulate cytokine signaling pathways in a murine erythroleukemia cell line.
Hexamethylenebisacetamide (HMBA) is a potent differentiation inducer of murine erythroleukemia cells. Immunoprecipitation followed by Western blotting with an anti-phosphotyrosine (P-Tyr) antibody revealed that HMBA increased P-Tyr levels and/or amounts of several proteins containing P-Tyr in F5-5, a murine erythroleukemia cell line. Among these proteins, we identified a Mr 130,000 protein to be Janus-activated kinase 2 (JAK2). HMBA induced tyrosine phosphorylation of JAK2 and signal transducers and activators of transcription 5 (STAT5) but not other JAKs or STATs. This phosphorylation was apparent 12 h after treatment, maximal at 24 h, and persisted for at least 96 h. Consistently, HMBA increased STAT5 DNA-binding activities. Other chemical inducers, DMSO and butyrate, also induced a sustained activation of JAK2/STAT5, whereas fetal calf serum and erythropoietin induced transient activation but not differentiation. Furthermore, overexpression of a dominant-negative form of STAT5 inhibited the chemically induced differentiation. These results suggest that persistent activation of the signaling pathway plays a significant role in the inducer-mediated differentiation. Our data also suggest that molecular mechanisms for the inducer-mediated activation of JAK2 are independent of cytokine receptor-mediated activation mechanisms. We tentatively conclude that cytokine signaling is an important target of chemical inducers in these cells.
Yamashita
T
T
Department of Hematology/Oncology, The Institute of Medical Science, The University of Tokyo, Japan. y-taka@hgc.ims.u-tokyo.ac.jp
Wakao
H
H
Miyajima
A
A
Asano
S
S
D000081:Acetamides / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002417:Cattle; D002454:Cell Differentiation / Q000187:drug effects; D016207:Cytokines / Q000502:physiology*; D004273:DNA, Neoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004921:Erythropoietin / Q000494:pharmacology; D005312:Fetal Blood; D005622:Friend murine leukemia virus; D053614:Janus Kinase 2; D004915:Leukemia, Erythroblastic, Acute / Q000235:genetics / Q000473:pathology*; D051379:Mice; D008894:Milk Proteins; D009363:Neoplasm Proteins / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects*; D015534:Trans-Activators / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000081:Acetamides; D000970:Antineoplastic Agents; D016207:Cytokines; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D008894:Milk Proteins; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D004921:Erythropoietin; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; C014026:hexamethylene bisacetamide